Year Percent 1950 28.78406 1955 27.56942 1960 26.08263 1965 24.23433 1970 23.44427 1975 23.94504 1980 24.36663 1985 25.62967 1990 26.89535 1995 28.70158 2000 30.54996 2005 30.96059 2010 33.23654 2015 28.73943 2020 29.76535 2025 32.49333 2030 33.14634 2035 34.09597 2040 33.05427 2045 31.48704 2050 29.9118 2055 28.7444 2060 28.14559 2065 27.47128 2070 26.58408 2075 25.52639 2080 24.48783 2085 23.71656 2090 23.23563 2095 22.9176 2100 22.61064